Atan

Function Atan

The Atan function computes an arctangent.

Performance:

	Default processor	Pentium® III processor	Pentium® 4 processor	Itanium® processor
vsAtan (HA version)	65.4	38.4	24.5	8.2
vdAtan (HA version)	87.7	87.6	75.7	13.5

Notes:
1) Units - CPE (Clocks per Element)
2) Performance was measured on "working" interval (double precision: [-10000,10000]; single precision: [0,5])
3) Data - vectors of 1000 elements with random generated numbers
4) "Default" means X87 code for all IA-32 processors
5) Performance of "default" version was measured on Pentium® III processor

Notes:
1) *        X87 code for all processors
2) **      Pentium® III processor
3) ***    Pentium® 4 processor
4) **** Itanium® processor
5) Logarithmic scale is used for "Vectors Size" axis

Maximal observed error for the whole function domain:

	Default processor	Pentium® III processor	Pentium® 4 processor	Itanium® processor
vsAtan (HA version)	0.61	0.88	0.88	0.50
vdAtan (HA version)	0.85	0.85	0.85	0.50

Notes:
1) Units - ULP (Units in The Last Place)

Special values:

Function	Input Argument	Result	Default processor	Pentium® III processor	Pentium® 4 processor	Itanium® processor
vsAtan/vdAtan (HA version)	0	0	+	+	+	+
	NaN (Both QNaN and SNaN)	NaN (Raise Invalid Exeption for SNaN)	+	+	+	+
	+ Inf	PI/2	+	+	+	+
	- Inf	- PI/2	+	+	+	+

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